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Abstract:

A matting agent useful for the preparation of matted coatings comprising,
inorganic oxide particulates and wax coated on the inorganic oxide
particulates, wherein the wax possesses a crystallinity of about 50% or
more.

Claims:

1. A matting agent useful for the preparation of matted coatings
comprising,inorganic oxide particulates; andwax coated on the inorganic
oxide particulates,wherein the wax possesses a crystallinity of about 50%
or more.

2. A matting agent according to claim 1, wherein said wax possesses a
crystallinity of about 55% or more.

3. A matting agent according to claim 1, wherein said wax possesses a
crystallinity of about 60% or more.

4. A matting agent according to claim 1, wherein said wax possesses a
crystallinity of about 70% or more.

5. A matting agent according to claim 1, wherein said wax possesses a
crystallinity of about 80% or more.

6. A matting agent according to claim 1, wherein said wax comprises
polyolefin.

11. A matting agent according to claim 1, wherein said inorganic oxide
possesses a median particle size of 2-12 microns.

12. A coating formulation useful for the preparation of matted coatings
comprising,inorganic oxide particulates;wax coated on the inorganic oxide
particulates; andcoating formulation components;wherein the wax possesses
a crystallinity of about 50% or more.

13. (canceled)

14. A coating formulation according to claim 12, wherein said wax
possesses a crystallinity of bout 60% or more.

15. A coating formulation according to claim 12, wherein said wax
possesses a crystallinity of about 70% or more.

16. A coating formulation according to claim 12, wherein said wax
possesses a crystallinity of about 80% or more.

23. A matted coating comprising,inorganic oxide particulates; andwax
coated on the inorganic oxide particulates,wherein the wax possesses a
crystallinity of about 50% or more.

24. (canceled)

25. (canceled)

26. (canceled)

27. (canceled)

28. (canceled)

29. (canceled)

30. (canceled)

31. (canceled)

32. (canceled)

33. A matted coating according to claim 23, wherein the abrasion
resistance of said coating using the Faber Test is less than 10 units of
gloss at 60.degree..

34. A matted coating according to claim 23, wherein the abrasion
resistance of said coating using the Faber Test is less than 5 units of
gloss at 20.degree..

Description:

FIELD OF THE INVENTION

[0001]This invention relates to wax coated inorganic oxide matting agents
useful for the production of coatings, coating formulations made
therefrom and the resulting matted coatings

BACKGROUND OF THE INVENTION

[0002]It is well known that micronised waxes will impart desirable
features to paint or lacquer film or coatings (e.g., flexibility, feel
and gloss). Inorganic oxide particulates have also been used to import
matting to the coating. When an inorganic oxide particulate is
coated/impregnated with wax a process usually performed by jointly
grinding the oxide particulate and wax in a fluid energy mill
(microniser), further product benefits are immediately available. The wax
can improve compatibility of the oxide particulate with the paint or
lacquer preventing interaction with other components in the formulation,
but another function is to prevent the formation of hard sediment during
storage, which is not redispersible. Whilst the mechanism by which this
protection is afforded is still not fully understood, its benefit to the
paint or lacquer manufacturer is widely recognized because, if hard
sediments that cannot be redispersed are formed, none of the benefits
described above can be realized.

[0003]Two types of wax-coated oxide particulates are generally disclosed
in the literature. GB Patent No. 798,621 discloses a silica-matting agent
produced by co-milling an intermediate density silica gel with a
microcrystalline wax in a fluid energy mill. GB Patent No. 1,236,775
teaches a silica matting agent can be prepared by treating precipitated
silica with an aqueous emulsion or dispersion of a wax, including
thermoplastic materials. The properties of the silica matting agents
prepared by the so-called "dry" co-micronising route have been further
improved by adding fatty acids (GB Patent No. 1,461,511) or synthetic
polyethylene waxes of varying molecular weight (U.S. Pat. No. 4,097,302)
to the microcrystalline wax before feeding to the fluid energy mill. The
former improves the dispersibility of the wax coated products, whereas
the latter shows products having enhanced settlement characteristics
compared with commercially available materials. The "dry" processing
routes described above use temperatures in excess of the melting points
of the waxes or wax blends whereas GB Patent No. 1,538,474 discloses a
process which can produce satisfactory wax coated silicas at micronising
temperatures of below 50° C., where functional waxes such as
montan acid ester are employed.

[0004]U.S. Pat. No. 5,326,395 describes a matting agent that utilizes a
ternary blend of waxes, including a hard microcrystalline wax, a
plasticizing microcrystalline wax, and a synthetic polyethylene wax, that
is coated on a silica particulate. U.S. Patent Application No.
2004/0047792 A1 relates to a wax coated precipitated silica matting agent
wherein the wax may include polyethylene waxes, Fischer-Tropsch waxes, or
silicone waxes.

[0005]U.S. Pat. No. 6,761,764 B2 describes the use of wax particles,
without an inorganic oxide component, for use as matting agents in
various coatings. The waxes used include a mixture of olefin waxes and
various other waxes.

[0006]There remains a need in the coating industry for an inorganic oxide
matting agent that provides acceptable matting properties while also
providing improved abrasion resistance and chemical stability.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007]FIG. 1 illustrates the influence by wax crystallinity on abrasion
resistance of the coatings according to the present invention.

[0008]FIG. 2 illustrates the abrasion resistance of coatings according to
the present invention compared with others.

[0009]FIG. 3 illustrates the matting efficiency of coatings according to
the present invention compared with others in wood lacquer.

[0010]FIG. 4 illustrates the matting efficiency of coatings according to
the present invention compared with others in UV lacquer.

[0011]FIG. 5 illustrates the chemical resistance of coatings of the
present invention as compared to others.

SUMMARY

[0012]The present invention relates to a matting agent useful for the
preparation of matted coatings including, inorganic oxide particulates
and wax coated on or impregnated in the inorganic oxide particulates,
wherein the wax possesses a crystallinity of about 50% or more.

[0013]The present invention also relates to a coating formulation useful
for the preparation of matted coatings including inorganic oxide
particulates, and wax coated on or impregnated in the inorganic oxide
particulates, wherein the wax possesses a crystallinity of about 50% or
more.

[0014]The present invention further relates to a matted coating including
inorganic oxide particulates, and wax coated on or impregnated in the
inorganic oxide particulates, wherein the wax possesses a crystallinity
of about 50% or more.

DESCRIPTION OF THE INVENTION

[0015]The terms referred to herein are to be given their accepted meaning
in the industry unless otherwise defined herein.

[0016]The term "particulate" is used to refer to solid, either singularly
or a collection thereof (e.g., powder) including spheroid(s), granule(s),
fragment(s), or pieces(s) of matter having regular or irregular shape or
surface.

[0017]The term "inorganic oxides" is used to describe a binary compound of
an element and oxygen and include metal and semimetal oxides. Examples of
such oxides may comprise SiO2, Al2O3, AlPO4, MgO,
TiO2, ZrO2, Fe2O3 or mixtures thereof. Mixed
inorganic oxides include SiO2, Al2O3, MgO, SiO2,
Al2O3, Fe2O3 etc., which may be prepared by
conventional preparation techniques (e.g., coblending, coprecipitating,
cogelling etc.). The oxides may be in a variety of forms, including
gelled, precipitated, fumed, colloidal, etc.

[0019]In one embodiment, the present invention relates to matting agent
useful for the preparation of matted coatings comprising inorganic oxide
particulates and wax coated on the inorganic oxide particulates, wherein
the wax possesses a crystallinity of about 50% or more. The wax may
possess a crystallinity of about 55% or more, preferably 60% or more,
more preferably 70% or more, and even more preferably 80% or more. In
another embodiment, the wax possesses a crystallinity of 90% or more
(e.g., 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, or 100%). Crystallinity of
the polymer is measured by differential scanning calorimetry using ASTM E
793 (1985 (Rev. 1989)).

[0020]Waxes of the present invention having the crystallinity described
herein include polymers that possess crystalline and amorphous regions,
if the crystallinity is less than 100%. The polymers of the present
invention may also be described as isotactic or syndiotactic, as compared
to atactic polymers, that is, the polymers possess regular, and not
irregular arrangement of its atoms or pendant groups. For example, highly
crystalline (e.g., above 50%) polymers include polyolefins, polystyrene,
polyamides, polyketones, polyesters, and the like. Preferably, the
polymer is a polyolefin, since these polymers melt at lower temperatures.
Polyolefins of the present invention may include polyalkylenes, such as
polyethylene, polymethylene, polypropylene, polybutene and the like, or
mixtures thereof. More preferably, a wax of the present invention may be
isotactic and/or syndiotactic polyethylene, polypropylene or mixtures
thereof, and are even more preferably of the polyethylene type. Suitable
waxes contain regular polymer chains enabling a cristallinity of more
than 90%. Suitable waxes have a weight-average molar mass from 1000 to 30
000 g/mol, with a drop point of 90 to 140° C., preferably from
110° C. to 140° C. The waxes have melt viscosities,
measured at a temperature 140° C. of not more than 1000 mPas,
preferably from 10 to 500 mPas.

[0021]The polymers of the present invention may be synthesized using any
conventional method that provides crystallinity of more than 50%. For
example, polyolefins may be produced using Ziegler-Natta polymerization
or by the metal-organic catalysis polymerization. Preferably, the metal
organic catalysis polymerization is of the metallocene type. Such
processes are described, for example, in U.S. Pat. Nos. 5,081,322;
5,643,846; 5,919,723; 6,194,341; and 6,750,307.

[0022]The inorganic oxide of the present invention may include a variety
of oxides as mentioned herein. However, in one preferred embodiment, the
inorganic oxide is silica. A description of this embodiment follows, but
any inorganic oxide may also be used instead of silica.

[0023]The silica used to prepare the invention can be that used to prepare
conventional porous silica matting agents, provided the silica has a pore
volume in the range of 0.8 to 2.4 cc/g. Preferably, the pore volume of
the silica is in the range of 0.9-1.2 cc/g. The pore volume referred to
herein is determined by nitrogen porosimetry, described later below.

[0024]Silica gels are preferred. Hydrogels, xerogels and aerogels are all
suitable. The general procedure to prepare inorganic gels is by the acid
neutralization of salt solutions of metals or metalloids, which,
thereafter upon standing form hydrogels. The hydrogels must then be
washed to remove the relatively high concentration of soluble salts.
Treatment during this washing stage determines physical properties, such
as porosity, of the final product. The techniques for obtaining those
properties are known. For example, final gel pore volumes and surface
areas are dependent upon the pH and temperature of the wash solution, the
rate of wash, the particle size of the hydrogel, and the duration of
wash. Generally, pore volume can be limited by shortening the duration of
the washing periods. However, the specific washing conditions can vary
depending on the particular inorganic hydrogel used, and are not per se
critical to the invention, provided that the aforementioned pore volumes
are developed in the final gel. As mentioned above, those skilled in the
art are familiar with these washing conditions and are readily able to
determine suitable washing conditions in which to form the desired pore
volumes for use in this invention. For example, silica gels washed at a
starting pH of 3-5 at 50-90° C. for 5-25 hours form gels
(aerogets) having pore volumes in the aforementioned range.

[0025]Particularly suitable silicas include hydrogels used to make
commercially available silica matting agents such as the Syloid®
matting agents from W. R. Grace & Co.-Conn.

[0026]The wax-containing matting agent of this invention can be prepared
by conventional co-milling processes in which the wax is melted
simultaneously with the comminution of the silica to the desired particle
size of about 2 to 12 microns. Such a process is most effectively carried
out in a fluid energy mill or microniser such as the Alpine® mill
available from Hosokawa Micron Limited and the Condux® universal mill
available from Netzsch, Inc. The operating temperature can then be varied
according to the requirements of the wax. The inlet temperature of the
air being supplied to the fluid energy mill should at least be high
enough to ensure the wax melts within the residence time profile of the
milling equipment. The wax is added to the mill so that the final product
has a wax content of 15 to 30% by weight.

[0027]Another embodiment according to the present invention relates to a
coating formulation useful for the preparation of matted coatings
including inorganic oxide particulates, wax coated on the inorganic oxide
particulates, and other coating formulation components, wherein the wax
possesses a crystallinity of about 50% or more.

[0029]Another embodiment of the present invention regards matted coating
including inorganic oxide particulates and wax coated on or impregnated
in the inorganic oxide particulates, wherein the wax possesses a
crystallinity of about 50% or more.

[0030]The coating is prepared by utilizing the coating formulations
described herein. Initially, the matting agent of the present invention
is prepared by blending the inorganic oxide with the wax in a mixer
(e.g., Henschel mixer) for a period of time (e.g., 10 to 20 minutes) and
at a speed (e.g., 2000 to 3000 rpm) that uniformly blends the oxide-wax
mixture. The mixture is then placed in a mill (e.g., fluid energy mill
such as Alpine AFG 100 available from Alpine AG so as to allow the wax to
impregnate and coat the oxide, and to provide a uniform and desirable
particle size. The milling is typically performed at a temperature of 50
to 200° C. for a period of 10 to 15 minutes per 600 gr.

[0031]Subsequent to the formation of the matting agent, the coating
formulation is prepared by dispersing the matting agent in ready to use
coating, including lacquer, paint, varnish or ink using a mixer (such as
a Dispermat CN10-F2 mixer available from VMA-Getzmann GmbH) at a speed
(e.g., 1000 to 5000 rpm) and period of time until the matting agent is
well dispersed (e.g., for a period of 5 to 30 minutes). The coating may
then applied at a typical thickness (e.g., 25 to 100 micron) onto a
substrate, such as wood, metal, plastic, etc. using an Erichsen coater,
such as a K-Control Coater K101 available from Erichsen GmbH & Co. KG.
The coating is then dried for a period of time (approximately 24 h) at
room temperature.

[0032]The matting agent according to the present invention provides
improved abrasion resistance over other coatings made with conventional
matting agents. For example, reduction in gloss units for a coating
including a matting agent of the present invention after subjecting the
coating to the Abrasion Test as defined herein is less than 10 units at
60° and 5 units at 20°, preferably less than 7 units at
60° and 4 units at 20°, more preferably less than 5 units
at 60° and 3 units at 20°, and even more preferably less
than 3 units at 60° and less than 2 units at 20°.

[0034]While the invention has been described with a limited number of
embodiments, these specific embodiments are not intended to limit the
scope of the invention as otherwise described and claimed herein. It may
be evident to those of ordinary skill in the art upon review of the
exemplary embodiments herein that further modifications and variations
are possible. All parts and percentages in the examples, as well as in
the remainder of the specification, are by weight unless otherwise
specified. Further, any range of numbers recited in the specification or
claims, such as that representing a particular set of properties, units
of measure, conditions, physical states or percentages, is intended to
literally incorporate expressly herein by reference or otherwise, any
number falling within such range, including any subset of numbers within
any range so recited. For example, whenever a numerical range with a
lower limit, RL, and an upper limit RU, is disclosed, any
number R falling within the range is specifically disclosed. In
particular, the following numbers R within the range are specifically
disclosed: R=RL+k(RU-RL), where k is a variable ranging
from 1% to 100% with a 1% increment, e.g., k is 1%, 2%, 3%, 4%, 5% . . .
50%, 51%, 52% . . . 95%, 96%, 97%, 98%, 99%, or 100%. Moreover, any
numerical range represented by any two values of R, as calculated above
is also specifically abrasive wheels rotating in clockwise fashion at a
speed of 60 rpm with a pressure applied to the test cards of 9N. The
abrasion medium on the wheels is 3M Scotch Brite fiber web CF-HP Typ 7498
(F-SFN). The cards are submitted to 500 rpm. The gloss level at
20° and 60° is measured before and after the Taber Test and
the change in gloss units is determined. A small change in gloss units
indicates good abrasion resistance. The results are set forth in Table 2
and in FIG. 2.

[0041]The results in Table 2 and FIG. 1 indicate that when particle size
and wax content are kept relatively constant, a matting agent having a
high crystallinity wax in the range of the invention has better abrasion
resistance than a matting agent having a low crystallinity wax outside
the range of the invention. Compare Invention 1 and 2 with COMP 1-3,
where the abrasion resistance of the coating made with the matting agent
of the present invention is at least double that of other matting agents.

[0042]It has also been unexpectedly found that abrasion resistance is
enhanced when using matting agents having a smaller APS at the lower end
of the particle size range claimed for this invention. See FIG. 2 where
coatings having an APS of 6 microns have a much lower abrasion resistance
than coatings having an APS of 8 microns.

[0043]FIG. 3 shows that the matting agent of the present invention (red
line) provides coatings with matting efficiency at least as equivalent of
coatings made with conventional matting agents. The samples are in mixed
into Lacquer 2 as described above in Examples 1-5. The light blue line
shows the matting efficiency of a commercial organic matting agent,
Pergopak M3, available from Deuteron GmbH. The yellow line shows a
commercial gel based matting agent, Fuji Sylysia 276, available from Fuji
Sylysia Chemical, Ltd., and the green line shows a commercial silica gel
matting agent, Syloid ED52, available from W. R. Grace & Co. The dark
blue line shows the efficiency of a commercial precipitated silica
matting agent, Acematt OK412, available from Degussa AG.

[0044]FIG. 4 shows the matting agent of the present invention (red line)
in comparison to other commercial matting agents when used in Lacquer 1.
The samples are in mixed into Lacquer 1 as described above in Examples
1-5. The light blue line shows the matting efficiency of a commercial
organic matting agent, Pergopak M3, available from Deuteron GmbH. The
yellow line shows a commercial gel based matting agent, Fuji Sylysia 276,
available from Fuji Sylysia Chemical, Ltd., and the green line shows a
commercial silica gel matting agent, Syloid ED52, available from W. R.
Grace & Co. The dark blue line shows the efficiency of a commercial
precipitated silica matting agent, Acematt OK412 available from Degussa
AG.

[0045]The chemical resistance of these different matting agents are tested
by dispersing them into Lacquer 1 using a Dispermat VMA available
Getzmann 3000 rpm for 10 minutes. The amounts of matting agent added
depend upon the gloss achieved and are set forth in Table 3. The lacquer
is applied as a film on the black test cards at a thickness of 100 μm
using a K-Control Coater "K101" available from Erichsen. The film is then
dried at 45° C. for 20 minutes in a LUT 6050 drier available from
Heraeus. Subsequently, the film is irradiated with 2 UV light for 10
minutes using polymerization equipment Typ M-20-2*1-TR-Ss-SLC available
from IST. After one week at room temperature, the chemical resistance of
the coatings is tested using the different liquids set forth in FIG. 5.
The method is described in DIN EN 12720, DIN 68861-1.

[0046]FIG. 5 shows an unexpected effect that the matting agents of the
invention provide coatings with improved chemical resistance over
coatings made with conventional matting agents. For example, non-matted
waterborne coating results in blister formation with water, red wine, and
ink; with good resistance against tee, coffee and
Na2CO3-solution. A coating made with SYLOID ED52 as the matting
agent is very resistant against water, coffee, tea and red wine; and
possessed less resistance against ethanol and ink; formed blisters with
beer only; and moderate brightening of the stains. Silica gel coatings
resulted in the general tendency to form blisters with most test
substances. Coatings made with precipitated silica matting agent resulted
in the destruction of film by coffee, ink, red wine and water; complete
film destruction by ethanol; and the formation of very large blisters.
Coatings made from fumed silica matting agent yielded poor resistance
against water, coffee, tea, and beer; destruction of film by red wine,
ink and ethanol; and the formation of large number of blisters and white
stains. Organic matting agent coatings provided generally poor resistance
against most test substances; destruction of film by water, coffee, red
wine and beer; and the formation of large number of blisters; and very
bright stains. Coatings made from the matting agent of the present
invention provides the most improved performance, including high
resistance against red wine and beer; good resistance against water,
coffee, tea with slightly less resistance against ethanol and ink; no
formation of blisters; and moderate brightening of the stains.